A radiation system includes a first ring, a radiation source capable of providing radiation suitable for treating a patient, the radiation source secured to the first ring, a second ring located behind the first ring, and an imager secured to the second ring. A radiation system includes a first device having a radiation source capable of generating a radiation beam suitable for treating a patient, and a second device having imaging capability, wherein the first device is oriented at an angle that is less than 180.degree. relative to the second device. A radiation system includes a structure having a first opening, a radiation source rotatably coupled to the structure, an imaging device rotatable relative to the structure, and a processor for controlling a rotation of the radiation source and a rotation of the imaging device, wherein the radiation source is rotatable relative to the imaging device.